Previous results on the influence of water pressure and velocity on flow-type cavitations erosion, i.e. an increase in erosion rate with increasing velocity and peaking of erosion rate as a function of pressure, were confirmed by measurements with a rotating-disc test rig. Owing to the importance of exercising control over the cavitations geometry in hydraulic equipment, the effect of pressure and velocity on the position and shape of the cavitations erosion zone was systematically studied. The observed geometry of the erosion zone, as well as the wear rate behaviour, was explained in terms of the change in the cavitations-inducing pressure gradient with pressure and velocity.